This invention relates to fluid supplying devices equipped with peristaltic pumps, and more particularly to a fluid supplying pump by which a desired amount of fluid can be obtained.
A peristaltic pump has been extensively employed for blending or supplying reaction raw material, catalyst, coloring agent, photosensitive agent, ink, paint, paste material, resin material, oil, flux, lubricant, cosmetic material, adhesive, food material, etc., because it needs no operating pumping section in the path of fluid. Therefore, the fluid is never brought into contact with such a pumping section, which maintains the characteristic of the fluid unchanged.
In the case where only a peristaltic pump is used, an amount of fluid per unitary time delivered under pressure can be determined. However, it is difficult to discharge a desired amount of fluid.
In order to overcome this difficulty, several fluid supplying devices provided with peristaltic pumps which can discharge a desired amount of fluid have been proposed in the art.
For instance, such a device has been disclosed by Japanese Patent Application Laid-Open No. 41903/1974. In this device, a cam plate having cam sections is mounted on the drive shaft of a peristaltic pump connected to an electric motor and the cam sections are detected by a detector so that the number of cam sections thus detected is applied to a counter. When the count value of the counter reaches a value preset in a manual preset device, a switch connected to the electric motor is opened to stop the motor. As a result a predetermined amount of fluid is delivered; that is, a necessary amount of fluid can be delivered without monitoring it.
Furthermore, U.S. Pat. No. 3,277,356 discloses a fluid supplying device in which a relay is connected to an electric motor operating a peristaltic pump so that the operation (drive and stop) of the peristaltic pump is controlled by the on-off operation of the relay. Swinging pins are connected to the drive shaft which connects the peristaltic pump to the electric motor in such a manner that the pins are rotated for a predetermined distance according to the rotation of the drive shaft. In addition, a pull switch operating the relay is disposed at the position of passage of the pins in such a manner that the position of contact between the switch and the pins can be changed. Thus, a desired amount of fluid is discharged.
In a fluid supplying device disclosed in British Pat. No. 1,216,327, at least three rollers adapted to depress an elastic tube are rotated around one axis by an electric motor. A plurality of stationary contacts arranged in circular form are disposed at the positions of passage of a group of electrical sliding contacts rotated with the rollers so that the sliding contacts can easily slide. Operating signals forming binary codes are supplied to the stationary contacts and are read by the sliding contacts. The code thus read is compared with a code set in a manual digital switch. When both are coincident with each other, the motor is stopped, and a desired amount of fluid has been discharged.
However, these conventional fluid supplying devices are still disadvantageous in that it is impossible to obtain different amounts of fluid successively by a single adjustment of the setting of the device.